Composition of matter



Patented Jan. 22, 1946 Firestone Tire &, Rubber Company, Akron, Ohio, acorporation of: Ohio No Drawing. Original application September 20,

1941, Serial No. 411,719. Divided and this application May 25, 1945,Serial No. 595,873

4 Claims.

This invention. relates. to: the vulcanization oirubber, and: relatesespecially to: a new class: of chemical; compounds which. are=valuab1e=accelenters; for. thevulcanization ofirubber; or rubberlike substances.This specification-a division y copending application Serial.No; 41',719, filed September I941, now-Patent.: Number 2,381,384.

Itisa primary object: ofzthe. present invention; to; provide, a new.class of accelerators for the vulcanization of; natural or,syntheticrubber.

Another object is to provide a new group of delayed action rubbervulcanization accelerators.

The above andfurther objects will be manifest in the description of theinvention which follows.

Ithas beenfoundthat members of anew class of, chemicalcompounds are veryeffective in accelerating the vulcanization of natural or syntheticrubber. The new compounds'may-be. convenientlyprepared. by oxidizing amixture of an aromatic Z-mercaptothiazole andan hydroxyalkyl primaryamine. The preparative oxidation reaction may be carried out by treatinga mixture of the merca'ptothiazole and an excess of the amine inanalkaline aqueous medium with one of the following oxidizing agents;chlorine, bromine, iodine, hypochlorous acid, hypobromous acid,hypoiodous acid, and alakli metal and alkaline earth metal salts of saidacids. The oxidation reaction is believed to comprise the direct actionof a hypohalous acid, or an alkali metal or an alkaline earth metal saltthereof, on a mixture of the mercaptothiazole and one equivalent of theamine. The desired substances produced by this oxidation reaction areorganic compounds containing nitrogen, sulfur and oxygen.

This new class of accelerators is believed to possess the following typeformula:

wherein Ar is an orthoarylene radical, R and R are hydrogen, alkyl orhydroxyalkyl radicals and R" is an hydroxyalkyl radical. Thus, the newcompounds are considered to be derivatives of sulfenamide (HSNHz).Examples of orthoarylene radicals comprise benzo, l-phenylbenzo,6-phenylbenzo, naphtho, and homologs or the various ring substitutionproducts of these radicals; as typical ring substituents there may bementioned nitro, halogen, hydroxy and alkoxy groups. Examples of alkylradicals include methyl, ethyl, propyl, butyl, amyl, hexyl, heptyl,octyl and similar radicals. Examples of hydroxyalkyl radicals includehydroxymethyl, alpha-hydroxyethyl, beta-hydroxyethyl and similarradicals.

The following specific example. is given in further illustration of theinvention.

Example A solution was prepared containing 10 grams ofmercaptobenzothiazole, 4.8 gramsof sodium hydroxide and 7 grams ofethanolamine in a volume'of 350 cubiccentimeters. Into this solution; atroom temperature, there was slowly dropped, with stirring, an iodinesolution containing 15 grams of iodine and 15 grams of potassium iodidein a volume of 150 cubic centi- A-white solid. precipitated. during theThe above reaction product was tested as a rubber vulcanizationaccelerator by comparing it with the standard accelerator,mercapt'obenzo thiazole, in the following'rubberi'ormula:

Ingredients 32 2 3 Rubber (smoked sheets) 100. 00 S fur 3. 00 Zincoxide. 5. 00 Stearic acid 1.10 Accelerator 0.

The two rubber compositions, so formulated, were vulcanized by beingheated at 280 F. for 20, 30 and 60 minutes, and the following physicaldata were obtained on the vulcanized compositions:

Modulus of Tensile strength in Accelerator ticity in lbs/in. at zelongation of 600% at break Cure in minutes 20 3O 60 20 30 60Mercaptobenzothiazole 700 700 750 2,425 2, 550 2,675N-(letafhgadroxyethgb- 2- n 0 may su enn amid: 1,575 1,700 1,550 3,4503,075 3,3a0

The above results clearly show that the sulfenamide derivative is a veryeffective rubber accelerator, which imparts consistently higher modulusand tensile characteristics to a rubber composition than does thestandard accelerator, mercapto-benzothiazole. Similar results areobtained by the use of other sulfenamide derivatives of the same class,such as N-(alpha,alpha dimethyl-beta-hydroxyethyl) -2-benzothiazylsulfenamide of the formula and N- alpha-methyl-alpha- (hydroxymethyl)beta-hydroxyethyl]-2-benzothiazyl sulfenamide of the formula These twoderivatives may be prepared by applying the general oxidation reactionmentioned above, respectively, to a mixture of mercaptobenzothiazolewith 2-amino-2-methyl-l-propanol and to a mixture ofmercaptobenzothiazole with 2-amino-2-methyl-1,3-propandiol.

The preferred class of sulfenamide derivatives may be prepared by othermethods than those mentioned hereinabove, as will be apparent to oneskilled in the art. For example, a mixture of an aromaticZ-mercaptothiazole and an hydroxyalkyl primary amine may be oxidized byhydrogen peroxide or other conventional oxidizing agent. The inventionis not limited to derivatives prepared in accordance with any paralsoexcellent resistance to deterioration on aging or flexing and lowhysteresis properties. Although the new accelerators cause rapidvulcanization of rubber compositions at usual vulcanizing temperatures,they are of the delayed action type and do not cause set-up orpre-vulcanization of the rubber under ordinary processing conditions andtemperatures. Moreover, the new class of accelerators may be used incombination with other accelerators, such as a guanidine (e. g.,diphenylguam'dine) or a mercaptothiazole derivative (e. g.,mercaptobenzothiazole or dibenzothiazyl disulfide) in order to producerubber compositions having special vulcanization characteristics, suchas the ability to vulcanize completely at abnormally low temperatures.

Although sulfur has been given as'the only example of a vulcanizingagent, other known vulcanizing agents may be used in the present methodof vulcanizing rubber.

What is claimed is:

1. N- (alpha,alpha-dimethyl-beta hydroxyethyl)-2-benzothiazylsulfenamide.

2. N-[alpha-methyl-alpha -(hydroxymethyl) beta-hydroxyethyl]-2-benzothiazyl sulfenamide.

3. A compound having the formula wherein Ar is an orthoarylene radical,R and R are selected from the group consisting 01' hydrogen, alkylradicals and hydroxyalkyl radicals, and R is an hydroxyalkyl radical. Iy

4. As a new chemical product 5 hydroxy ethyl amino thio benzothiazolepossessing the structural formula of a EDWARD L. CARR.

